1. Field of the Invention
The present invention relates to an image forming apparatus in which a unit including a transfer roller is constructed to be capable of being pulled out from a main body frame and a jam processing is facilitated, and an operation method of the image forming apparatus.
2. Description of the Related Art
In an image forming apparatus such as a laser printer or a digital copier, a toner image formed on an intermediate transfer medium by an image forming section provided in a main body frame is transferred onto a sheet conveyed through a sheet conveyance path. In this case, the toner image on the intermediate transfer medium is transferred onto the sheet by a transfer roller which nips the sheet as a print object and comes in press contact. As an image forming apparatus as stated above, there is one disclosed in JP-A-2004-118202, in which a duplex unit is disposed near a transfer roller. As is well known, the duplex unit is for performing duplex printing by reversing a sheet on one side of which an image is transferred and fixed and by again feeding it to a transfer roller portion.
In the image forming apparatus as stated above, for a jam processing or the like, the duplex unit is constructed to be capable of being pulled out from the main body frame. That is, when a jam occurs, the duplex unit is pulled out from the main body frame, and the space generated by the pulling is used, so that the sheet conveyance path formed in the main body frame can be easily visually confirmed from the outside. In this case, the transfer roller is attached to the side of the duplex unit, and the transfer roller is also pulled out from the main body along with the pulling of the duplex unit.
After the jam processing, the transfer roller, together with the duplex unit, is again mounted to the main body frame, however, since a force in a press contact direction applied to the transfer roller is applied as a reaction force to the mounting operation, it is difficult to perform the mounting operation. That is, the transfer roller always receives a pressing force by a spring or the like so as to come in press contact with the surface of an intermediate transfer medium across the sheet. However, when transfer is not performed, that is, when the sheet is not conveyed between the intermediate transfer medium and the transfer roller, the transfer roller is retracted to a separated position separate from the surface of the intermediate transfer medium. The retracting operation is performed such that a member for separating operation is protruded from the main body frame to push a lever member of applying the pressing force to the transfer roller.
When the foregoing transfer roller is mounted to the main body frame, transfer is not performed naturally, and accordingly, the member for separating operation provided on the side of the main body frame is in the protruded state. In this state, when the transfer roller is pushed to the side of the main body frame, the lever member of applying the pressure to the transfer roller comes in contact with the member for separating operation in the protruded state, is rotated in the direction opposite to the pressing force, and retracts the transfer roller to the separated position. That is, at the time point of completion of mounting to the main body frame, the operation is performed so that the transfer roller is retracted to the separated position.
The force to rotate the lever member against the pressing force by the contact with the member protruded from the side of the main body frame becomes the reaction force when the transfer roller is pushed to the side of the main body frame. Accordingly, it is difficult to perform the work of mounting the duplex unit including the transfer roller to the main body frame.